ENERGY FROM THE OCEAN:

1
ENERGY FROM THE OCEAN

• Waves
• Tides
• Temperature Differences
• Ocean Thermal Energy Converter

2
Sources of Energy

• The ocean can produce two types of energy
• thermal energy from the sun's heat
• mechanical energy from the tides and waves
• 70 of our planet is ocean, so ocean energy can
  be seen as a limitless energy source.

• The World Energy Council estimates that there is
  an accessible resource of two terawatts of
  renewable, clean energy available in the world's
  oceans. This is a potential resource equivalent
  to twice the world's current electricity
  generation.

3
Wave Energy

• Waves are caused by the wind blowing over the
  surface of the ocean. There is tremendous energy
  in the ocean waves.
• The total power of waves breaking around the
  worlds coastlines is estimated at 2-3 million
  megawatts. The energy from waves hold the
  greatest potential of the ocean energy sources,
  and wave power can be exploited in many more
  locations.
• Countries with the largest potential are those
  with large coastlines and strong prevailing
  winds.
• The west coasts of the US and Europe and the
  coasts of Japan and New Zealand are good sites
  for harnessing wave energy.

4
Methods of harnessing wave energy

• One way to harness wave energy is to bend or
  focus the waves into a narrow channel, increasing
  their power and size. The waves can then be
  channeled into a catch basin or used directly to
  spin turbines.
• As the water flows into and out of the basins it
  either directly activates a generator or
  transfers to a working fluid, water, or air,
  which then drives a turbine/generator.

5
Methods of harnessing wave energy

• Pelamis P-750 is an articulated 'snake' that
  floats on the ocean surface. Its articulated
  joints are connected to hydraulic rams that move
  with the wave motion, forcing hydraulic fluid to
  move through hydraulic motors that power electric
  generators.

• The AquaBuOY is a floating buoy structure that
  converts the kinetic energy of the vertical
  motion of oncoming waves into clean electricity.
  It converts the vertical bobbing motion of an
  anchored buoy into the movement of pressurized
  water that, in turn, moves through a turbine to
  make electricity.

6
Current Projects

• Wave Hub is a groundbreaking renewable energy
  project in the South West of England that aims to
  create the UK's first offshore facility for the
  demonstration and proving of the operation of
  arrays of wave energy generation devices.

7
Disadvantages
Advantages

• Waves are continuous and predictable
• Produces no liquid or solid pollution
• Many locations for energy production
• Almost no negative environmental impact

• Possible threat to navigation from collisions due
  to the low profile of the wave energy devices
• Interference of anchorage lines for commercial
  and sport-fishing
• Degradation of scenic ocean front views from wave
  energy devices located near or on the shore

8
Tidal Energy

• Tides are caused by the gravitational pull of the
  moon and sun, and the rotation of the earth.
• Locked within the rise and fall of tidal waters
  is an abundance of free energy.
• In order for tidal energy to work well, you need
  a large enough tidal range at least 10 feet
  to produce energy economically. There are only a
  few places where this tide change occurs around
  the earth.
• Tidal energy has been used since about the 11th
  Century, when small dams were built along ocean
  estuaries and small streams. The tidal water
  behind these dams was used to turn water wheels
  to mill grains.

9
Methods of harnessing tides

• 1) The simplest generation system for tidal
  plants involves a dam, known as a barrage, across
  an inlet. When tides comes in, the water can be
  trapped in reservoirs behind dams. Then when the
  tide drops, the water can be let out just like in
  a regular hydroelectric power plant. There are
  two-way systems that generate electricity on both
  the incoming and outgoing tides.
• 2) Tidal turbines are basically wind turbines
  that can be located anywhere there is strong
  tidal flow. They are essentially an underwater
  version of a horizontal-axis wind turbine.
  Because water is about 800 times denser than air,
  tidal turbines will have to be much sturdier than
  wind turbines. They will be heavier and more
  expensive to build but will be able to capture
  more energy.
• 3) A tidal fence is similar to a barrage and
  contains a series of gates that let water pass
  through. An advantage is that is it not as
  disruptive to the ecosystem as a dam.

10
Disadvantages
Advantages

• Reliable and predictable energy source the rise
  and fall of the tide driven by the steady motion
  of the moon unlike wind turbines which are at
  the mercy of the wind
• Very abundant energy in certain areas
• Produces no liquid or solid pollution
• Shelters the coast, useful in hurricane/cyclone
  prone areas and erosion zones

• Can change the tidal levels and increase
  turbidity in the water
• Installation and maintenance are very costly
• They can also affect boat navigation and
  recreation
• Time lag 12 hours between high and low tides
• Potentially the largest disadvantage of tidal
  power is the effect a tidal station can have on
  plants and animals in the estuaries

11
Current Projects

• The US has no tidal plants and only a few sites
  where tidal energy could be produced economically
  (Maine, Alaska). France, England, Canada, and
  Russia have much more potential.
• One facility, called the La Rance Station in
  France, has been running since 1966 and makes
  enough energy from tides (240 megawatts) to power
  240,000 homes.
• It is more than 10 times more powerful than the
  next largest tidal station in the world, the
  Canadian Annapolis station.

12
Ocean Thermal Energy Conversion (OTEC)

• OTEC systems use the ocean's natural thermal
  gradient to drive a power-producing cycle.
• It's warmer on the surface because sunlight warms
  the water. But below the surface, the ocean gets
  very cold.
• Power plants can be built that use this
  difference in temperature to make energy.
• As long as the temperature between the warm
  surface water and the cold deep water differs by
  about 20C (36F), an OTEC system can produce a
  significant amount of power.

• The need for a large temperature gradient limits
  use to tropical regions.

13
Ocean Thermal Energy Conversion (OTEC)

• Most OTEC systems are closed-cycle systems that
  use fluid with a low boiling point, such as
  ammonia, to rotate a turbine to generate
  electricity.
• Warm surface seawater is pumped through a heat
  exchanger where the low-boiling-point fluid is
  vaporized. The expanding vapor turns the
  turbo-generator.
• Then, cold, deep seawaterpumped through a second
  heat exchangercondenses the vapor back into a
  liquid, which is then recycled through the
  system.

14
Advantages

• Potential to produce massive amounts of
  electrical energy
• Produces desalinated water for industrial,
  agricultural, and residential uses
• Provides air-conditioning for buildings
• Produces no liquid or solid pollution
• Has significant potential to provide clean,
  cost-effective electricity for the future

Disadvantages

• OTEC plants are extremely expensive
• Current plants only achieve about 1-3 efficiency
• Limited geographic availability
• Electricity must also be transported to land
• It will probably be 1020 yrs. before technology
  is available to produce/transmit electricity
  economically from OTEC systems

15
Sources

• Energy Kids Page Energy Information
  Administration
• http//www.eia.doe.gov/kids/energyfacts/sources/re
  newable/ocean.html
• Renewable Energy World
• http//www.renewableenergyworld.com/rea/tech/ocean
  energy
• California Energy Commission
• www.energy.ca.gov/development/oceanenergy/
• http//www.energyquest.ca.gov/story/chapter14.html
  
• World of Renewables
• http//www.worldofrenewables.com/page.php?pageid5
  4
• Symscape Energy from the environment
• http//www.symscape.com/blog/energy_from_environme
  nt